Google Feed API is no longer available

With 2nd December 2015 fetching RSS Feeds via the Google Feed API (deprecated by April 2015) doesn't work anymore! Some of you may also received the error message that Google Feed API is no longer available. We were using it for our Blog and got this JSON Response:

At first we were looking for alternatives, until we realized we really just want to convert the RSS to JSON to use it in our JavaScript. What I consider to be the best solution (if you have access to the source content/server) is to change the response format at the origin.

How we fixed the problem

Our fastest and easiest solution: We installed the Wordpress Plugin Feed JSON so that our blog serves its feed also in JSON, like this: